Swan Hill and Robinvale Drainage Strategy

Background

Swan Hill Rural City Council (SHRCC) commissioned WMS Engineering to develop a comprehensive drainage strategy for the urban areas of Swan Hill and Robinvale.

This strategy aims to address stormwater management challenges caused by flat terrain, aging infrastructure, and increasing urban development.

Key Objectives

Assess current stormwater infrastructure performance.
Identify areas with stormwater drainage deficiencies.
Develop hydrologic and hydraulic models using TUFLOW.
Propose and evaluate mitigation options.
Engage with community and stakeholders.

Key findings

Both towns can experience flooding due to undersized pipes, blocked drains,lack of drainage infrastructure and pump station limitations.
The 2023 rain event in Swan Hill (80.6 mm in 9 hours) validated the 2% AEP (Annual Exceedance Probability) model.
Coincident storm events with high Murray River levels significantly worsens local drainage, especially in Swan Hill.

Community Engagement

19 attendees at drop-in sessions and 37 online survey responses.
Community input helped identify priority areas and validate model outputs.

View the Strategy

Due to the large file size - we have split the Strategy into Part One and Part Two.

** Please note:

Unfortunately the Appendix pages associated to the Swan Hill and Robinvale Drainage Strategy are too large to upload to be of a suitable resolution for viewing online.

Anyone wishing to view these appendix pages, please call into one of our customer service centres.

For all enquiries please phone: (03) 5036 23333.

Strategy Summary

Purpose

To address stormwater management challenges in Swan Hill and Robinvale by evaluating existing infrastructure, simulating flood risks, engaging community input, and identifying effective and prioritised flood mitigation options.

Key Components of the Strategy

Hydrologic and hydraulic modelling using Two-dimensional Unsteady FLOW (TUFLOW) for 1%, 2%, and 20% AEP events.

LiDAR, survey and flood data analysis to assess terrain and infrastructure performance.

Community consultation through drop-in sessions and online surveys to validate local flooding issues.

Mitigation option assessment to identify and prioritise cost-effective, high-benefit solutions.

Major Issues Identified

The flat terrain in both towns, combined with undersized or inadequate drainage infrastructure, contributes to ongoing drainage management challenges.
Localised drainage issues identified particularly in Swan Hill (e.g. Main Drain, Butterworth Street) and Robinvale (e.g. Robin Street).
Flooding events worsened by coincident river flooding and pump station limitations.
Swan Hill's November 2023 flood (80.6mm in 9 hrs) validated model accuracy.

Next Steps

Adoption of the Strategy and it's project recommendations.
Conduct detailed design and cost-benefit analysis
Prioritise high-impact projects for staged implementation

The strategy was developed to address long-standing stormwater management issues in both towns, including flat terrain, undersized and lack of infrastructure, and increased urban development, which have led to frequent stormwater drainage issues.

This strategy plans to provide a blue-print to future proof our municipality from storm events.

Hydrologic and hydraulic modelling using TUFLOW rain-on-grid simulations were used to assess existing drainage systems under various storm scenarios (1%, 2%, and 20% AEP events).

TUFLOW is widely used hydraulic modelling software that simulates how water moves over land and through drainage systems during flood or storm events. TUFLOW models are used to understand:

Peak flood depths and levels due to storms or riverine flooding.
Hazard classifications.
Velocity.
Duration of inundation.
Pipe and channel network capacity.

It models how water flows in two dimensions, meaning it can account for both the depth and direction of water movement across land surfaces - this is especially useful in flat or urban areas like Swan Hill and Robinvale.

Annual Exceedance Probability - this refers to the likelihood of a rainfall or flood event of a certain size occurring in any given year.

AEP is expressed as a percentage.
It describes how probable it is that a particular storm or flood event will be equaled or exceeded in any one year.

Common AEPS and what they mean:

AEP (%)	Equivalent Return Period (Years)	Meaning
1%	1-in-100 year event	There is a 1% chance of this event happening in any year
2%	1-in-50 year event	2% chance per year
5%	1-in-20 year event	5% chance per year
20%	1-in-5 year event	20% chance per year

The study focused on the urban areas of Swan Hill and Robinvale, both located along the Murray River in northwest Victoria.

Community engagement included drop-in sessions, an online questionnaire, and stakeholder meetings. Feedback helped to identify and confirm flooding hotspots and validate model outputs.

Key issues included:

Undersized and blocked pipes
Lack of drainage infrastructure
Inadequate pump station capacity
Flat terrain limiting drainage
Lack of formal drainage in some areas

In Swan Hill:

Charlie Gray Close, Butterworth Street, Swan Hill North Primary School, and the industrial estate near the Main Drain.

In Robinvale:

Robin Street, Ronald Street, and areas near the levee such as Lawrence and Alexander Streets.

Top recommendations include :

Robinvale: R02 (Refined Robin Street Upgrade), R05 (Ronald Street Upgrade with Swales and Pumps) page 137 of the Drainage Strategy.
Swan Hill: S03 (Main Drain Pump Station Upgrade), S05 (Butterworth Street Network), S01 (Werril Street Drainage Upgrade) page 137 & 138 of the Drainage Strategy.

Options were assessed based on flood reduction effectiveness (depth of flooding and inundation duration), cost, implementation feasibility, and community benefit. A traffic light system (High, Medium, Not Recommended) was used to prioritise them.

Page 134

To find out if your property is potentially affected, please refer to the mapping data included in the Drainage Strategy document. This mapping outlines areas that may be exposed to flooding in a 1% Annual Exceedance Probability (AEP) event.

What should I do if my property is listed as impacted?

Being within a potential flood-affected area does not necessarily mean your buildings are at risk. The actual impact depends on the difference between the floodwater height and your property’s floor level. In many cases, buildings remain unaffected.

If you are concerned or would like help assessing your property’s specific risk, please contact Council on (03) 5036 2333. Council may be able to assist you directly or connect you with the appropriate service.

Note: One of the strategy's key goals is to reduce how long and how deep storm-water sits in localised areas after heavy rainfall.

There is no evidence to suggest that properties identified in the strategy will be devalued. In fact, the strategy aims to improve stormwater management infrastructure, which can enhance property resilience and community safety.
These improvements may positively influence property value over time.

Council does not set or influence insurance premiums. These are determined by your provider based on many factors. If your insurer requires evidence of your property’s flood risk, you can supply data such as your floor level compared to the 1% AEP flood level, available within this strategy. Shopping around may also help, as many insurers offer competitive rates.

The strategy provides valuable technical data to inform future development in Swan Hill and Robinvale. Planning applications will continue to be assessed in line with local and state planning controls, but this strategy gives Council a clearer understanding of flood-prone areas. This helps ensure new developments are built in a way that avoids or minimises flood risk and supports long-term resilience for the community.

Council will:

Adoption of the Strategy and it's project recommendations.
Conduct detailed design and cost-benefit analysis
Prioritise high-impact projects for staged implementation

Let's talk

Swan Hill and Robinvale Drainage Strategy

Background

Key findings

Community Engagement

View the Strategy

Strategy Summary

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